Method of producing an insecticide



Patented Oct. 12, 1937 UNITED STATES PATENT OFFICE 2,095,464 METHOD orrnonuomc AN INSECTICIDE No Drawing. Application December 22, 1932,Serial N0. 648,441

. 2 Claims.

This invention relates to free-flowing salts and to methods of makingthe same. More particularly the invention is directed to the productionof free-flowing insecticides utilized in the dry 5 powdered form andapplied by dusting.

Insecticidal substances, such as sodium fluoride, have been heretoforeemployed to a considerable extent in relatively finely dividedcondition. Generally speaking, prior commercial products of this naturehave been such that the dry powder tends to ball up or pack and is notfree-flowing. Hence such productsmay not. be satisfactorily distributedby dusting from sifter cans and dust guns. Poisonous salts, such assodium fluoride, sodium silico fluoride, etc. are more or less widelyused as insecticides or insect powders for household purposes in whichinstances such substances are likely to get into the hands ofindividuals unaware of the toxic properties of the insecticides. usuallysold in the form of white powders which cannot be readily identifiedmerely by appearance, and-accordingly have been mistaken at times forflour, baking powder, etc. with disastrous results. For the purpose ofidentifying poisonous substances utilized as insecticides it has beenheretofore suggested to color the same to distinguish the insecticidefrom harmless substances. I

As one of theprincipal objects, this invention aims to provideinsecticides which are in finely divided condition and are readilyfree-flowing. A further particular object of the invention lies in theprovision of an economical method by which the insecticidal substancesmay be made free-flowing without interfering materially with theprocedure normally employed for the production of such materials. Thepresent improveof finely divided free-flowing insecticides having acharacteristic color appearance which will prevent such substances frombeing mistaken for non-poisonous materials. The process of the inventionalso includes a procedure by means of which the coloring material may beapplied to the insecticide salt during the manufacture thereofsubstantially without the use of additional steps other than thoseemployed in the manufacture of the insecticidal substances by the usualmethods.

Inaccordance with the invention, it has been found that salts, such assodium fluoride and similar materials used as insecticides or for otherpurposes where free-flowing properties in salts are desired, may berendered free-flowing by in- These products are ments additionallycontemplate the production.

corporating' therewith soapin relatively small quantities. Although thesoap may be admixed mechanically with the salt, it has been discoveredby the present improvements that the soap may be associated with salts,such as sodium fluoride and similar materials which are produced byprecipitation or crystallization from solution without in any mannersubstantially interfering with or interrupting the process of producingthe salts, by forming a solution of the. particular soap to be employedand applying the soap solution to the salts after separation of thelatter from the mother liquor in which they are formed, and while thesalts are still damp with wash water or mother liquor but prior to thefinal drying and grinding of the salts. In accordance with thispreferred mode of procedure, the salts while still damp or wet withmother liquor or washing liquid are mixed with a water solution of soap,and are thereafter dried to remove the adhering liquid carried by thedamp salts. Where it is desired to produce an insecticide containingcoloring matter in addition to having free-flowing properties, asolution of coloring material is likewise preferably added to the wetsalts just prior to drying. By operating in this manner, soap, andcoloring material if desired, may be associated with the insecticidesubstantially without use of operating steps other than those usuallyemployed in the manufacture of the salt.

In carrying out the invention, to produce freeflowing sodium fluoride,sodium fluoride is prepared inthe usual manner by adding soda. ash tohydrofluoric acid solution in amount suflicient to approximatelyneutralize the acid. The resulting finely divided precipitate of sodiumfluoride is then separated from the resulting mother liquor by anysuitable means, for example, acentrifuge, and the damp salt is passed toa drier by any suitable means, for example, a screw conveyor. A watersolution of a suitable soap, for example, a 10% solution of laundrysoap, is made up, and the solution added to the damp salt while thelatter is being passed from the centrifuge to the drier by the conveyor.The amount of soap solution added is regulated so as to include in theresulting product, when dried, the desired amount of soap.

By the present invention, it has been found that the incorporation inthe final product .of as little as about 0.25% by weight of soapproduces satisfactory results rendering the insecticide remarkablyfree-flowing and facilitating dusting of the same from sifter cans anddust guns. The

amount of soap associated with the insecticide may vary considerably.Good results may be obtained where the soap content of the product is aslow as 0.15%. However, it is preferred to include in the final productapproximately around .25% soap. Particularly satisfactory results may beobtained where this amount of soap is introduced in the form of asolution. Where a mechanical mixture of salt and soap is made, it may bedesirable to employ larger quantities of soap, say up to 1% by weight.Generally, it is preferred to use not less than about 0.15% by weight.Quantities of soap in excess of 1% may be employed where founddesirable.

Sodium fluoride formed as noted above by neutralization of hydrofluoricacid with soda ash comprises a major portion of sodium fluoride, andsmall amounts of sodium sulfate, sodium silico fluoride, sodiumchloride, sodium bicarbonate and water as impurities, the impuritiesresulting from the use of commercial hydrofluoric acid and soda ash.Generally speaking, in the manufactureof sodium fluoride by theprocedure contemplated by the present invention, the product producedcontains slightly in excess of 95% sodium fluoride, and the preferredembodiment of the invention comprises association of a desired amount'ofsoap with insecticidal compositions containing approx imately 95% sodiumfluoride. Hence, subsequent to addition of the preferred amount of soap,i. e., about .25%, the preferred products contain about say, 95% sodiumfluoride. The specific sodium fluoride content of the products is notcontrolling, and in .some instances the sodium fluoride content of theinsecticidal products may run as low as 85%, the balance includingimpurities derived from the raw materials employed in making the sodiumfluoride, and/or substances which may be purposely added to the productsto efiect dilution thereof. Where it is desired to make insecticidalcompositions having a sodium fluoride content substantially less thanapproximately 95%, suitable diluents, such as sodium sulfate, may beadded to lower the sodium fluoride content to the desired extent. Wherethe product is diluted, the diluting material may advantageously beadded to the salt as the latter in the damp condition passes from thecentrifuge to the drier. The diluting material thus becomes thoroughlyadmixed with the product.

Where it is desired to manufacture a freeflowing colored insecticide, awater solution of a dye, for example an alkali fast green dye, may beformed and added to the finelydivided salt as the latter is transferrredfrom the centrifuge to the drier. In this procedure also, the quantityof dye employed is regulated so as to give the desired color sought. Forexample, a satisfactory colored sodium fluoride may be obtained by usingan amount of a suitable water soluble dye equal to about two pounds ofdye in water solution to one ton of sodium, fluoride.

When the process of the invention'is carried out in such manner, theaction of the screw conveyor which moves the damp salt from thecentrifuge to the drier effects a. certain amount of mixing with thesalt of the soap solution, the dye solution, and the diluting'materialif used," while the subsequent agitation of thesalt in the drier eflectsthorough commingling with the sub:

stances involved. The soap and the coloring material, and dilutingmaterial if employed, are thus uniformly distributed throughout thesalt. The salt while being agitated is simultaneously dried, and may beheated to remove moisture and the procedure now employed in treatingsuch materials.

Soap may be incorporated with the salt in the dry form and not in watersolution. In this instance, the dried soap may be admixed by anysuitable means with the sodium fluoride after the latter has beendischarged from the drier. It has been found, however, that the resultsobtained by incorporating the soap in the dry pow- .dered condition withthe salts are not as satisfactory as where the soap is introduced in theform of a soap solution while the salts are in the damp condition. Itappears that where the soap is added to the salt in water solution, asoap film is formed about the individual particles of the salt whichfilm seems to maintain the salt particles in the separated condition,preventing the fine material constituting the products from clingingtogether. Irrespective of whether or not a film of soap-is actuallyformed around the individual particles of the product, in accordancewith the invention it has been found thatthe best ,results are obtainedwhere soap is added to the damp salt in the form of a water solutionrather than incorporated in the dry condition with the finished product.

While for illustrative purposes, the invention has been described inconnection with the manufacture of sodium fluoride, the principles ofthe invention may be utilized in the production of other salts which inuse are distributed from sifter cans, dust guns and the like. In placeof laundry soap other soaps may be used if desired.

I claim:

1. The method of producing free-flowing soand puldium fluoride whichcomprises precipitating so-..

dium fluoride from solution, separating the bulk of the solution fromthe precipitated salt to form a body of salt in damp condition, forminga water solution of soap, then adding said solution to theprecipitatedsodium fluoride while the salt is still damp from theseparator, and then drying the sodium fluoride. Y

2. The method of producing free-flowing relatively water insolubleinsecticidal salts which comprises forming from a solution the waterinsoluble precipitate of the salt, separating the precipitated salt fromthe bulk of said solution to form abody of salt in damp condition,forming a water solution of soap, then adding said solution to theprecipitated salt while the salt is still damp after the separatingoperation, and then drying the salt.

NELSON A. CHESNU'I'I. JR.

